SE534692C2 - Method for continuous and proportional addition of lime - Google Patents

Description

The content of the present application is a further development of the NO application 19980435, previously filed by the present applicant P R Stephansen, and is hereby incorporated by reference.

During operation of a limescale extinguisher, and similar systems, contaminants and dust can lead to the accumulation of limestone, which affects the extinguishing and can lead to blowouts at high temperatures. A new method of immediate cleaning is provided which prevents the accumulation of limestone and the disadvantages this leads to.

It is a further object of the invention to provide a method which utilizes the system in the extinguisher in such a way that it is not necessary to have buffer tanks between the extinguishers and the water flow through a plant, which has proved to be a great problem. Thus, a simplified supply to the plant is provided, without intermediate storage in dosing tanks, and thus accumulation of limestone in the other tanks and in the system is prevented. This has previously proved to be difficult, due to dosing problems, and in this respect it has been common to install, for example, a fate meter to measure and control through fate.

Said plants can be many types of plants or combinations of plants, which use the addition of lime, including plants for water preparation for both drinking water and agriculture, plants for sewage treatment, plants for sludge landfill, etc. etc.

A closed system is provided which does not produce dust and in view of the immediate cleaning an installation with at least reduced maintenance is provided due to the reduction of the accumulation of limestone.

The present invention is characterized in that a first extinguisher empties completely extinguished and diluted lime sludge according to the weight principle proportional to the water throughput of the plant, until a predetermined sludge weight mass remains, which is used for mixing with the next batch, a second extinguisher, which is ready for its emptying. begins to discharge completely extinguished and diluted lime sludge according to the weight principle proportional to the water through-hos of the plant, when the first extinguisher has finished emptying, until a predetermined sludge mass remains, which is used for mixing with the next batch, and after flushing with flush water via valves at each extinguisher is started 20 30 35 534 B92 3 production of a new batch, which is ready for its emptying sequence when the active extinguisher has finished its emptying.

The respective extinguishers are emptied directly to the water flow through the system, without the use of intermediate buffer or dosing tanks.

The invention will be described with the aid of the accompanying figure which shows an embodiment of a lime extinguishing device.

In carrying out the method according to the invention for batch hot quenching of burnt lime, a lime quenching device is used as shown and described in detail in the said NO patent application 19933084, to which reference is made.

It should be pointed out that values for given weights, volumes, temperatures, times, etc. are given as examples and the mentioned values must therefore not be considered as absolute.

A preferred lime extinguisher device, which is shown schematically in Figure 1, essentially comprises a lime extinguisher 2 with an effective volume, for example, of 2100 l (weight scale range 0-2500 kg), with a cylindrical upper section 53 and a conical lower section 54, mounted on three load cells 7 for batch weighing of water and lime, and with a mixer 16 with a specially designed mixing body and drive motor 18, rotation monitor 20 and also a water jet driven combined vacuuming / dam device / partition 15 which is fed with water through a pipeline with a valve 17, where the extinguisher 2 receives water through a pipeline with valves 8 and 9. The extinguisher cover 4 is connected to a specially designed water outlet preventing valve which also separates the wet and dry lime zone. The extinguisher is connected to a lime silo 1 with a level indicator and also an alter 52 with a drive motor 51 for mechanical cleaning. The silo can hold 80 t of burnt lime, for example with a bulk density of 1.1 (weight scale range 0-90 t), and is equipped with load cells to read the weight. The amplifiers of the load cells emit a 4-20 mA signal to a PLC. The silo can also be equipped with three air activators that start and follow a given cycle, if the dosing time for the screw conveyor is exceeded.

The silo is filled with lime through the inlet pipe from, for example, a tanker. The weight of the amount in the silo is displayed from a cabinet at the silo filling site. When 95% of the weight (AH) has been reached, an alarm in the form of an audible / light signal is issued as a warning that the filling must be stopped. The audible alarm can be set from the cabinet and / or automatically by means of the PLC, for example after three minutes. At 100% weight (AHH), a filling valve closes automatically and the charging of lime is stopped. While the valve is closed, a red warning light in the cabinet indicates that the silo cannot be refilled. The filling valve can be controlled manually from the panel in the control center.

Load cells mounted on the silo send out an alarm signal and a trigger signal: - at z AH Alarm. The operator is alerted to a high level in the silo. - at z AHH Warns the operator and closes the inlet valve. - at s ALZ Alarm. Low level in the silo.

The filter motor is preferably equipped with a safety switch and a service facility (automatic / manual).

After the filling of lime in the silo has been completed, the filter engine 51 is started manually from a local cabinet. A signal is sent from the cabinet to an external PLC which starts the motlter motor and monitors the operating condition of the motor. Filter motor 51 stops automatically after three minutes.

Example 1. Start button in a local cabinet is activated 2. The filter motor 51 starts and the operating light in the cabinet lights up. 3. The filter motor stops after about three minutes Lime is transferred with the screw conveyor 6 from the silo 1 to the extinguisher 2 with the damper valves 11 and 12 open. Extinguishing is initiated by manually extinguishing the first batch. The addition of lime then takes place automatically, whereby the extinguisher 2 is filled with a predetermined amount of dilution water. The extinguisher is then emptied to a predetermined remaining amount, in which the next batch of lime is to be extinguished.

The lime extinguishing temperature is determined by the ratio between the remaining number of kilos of diluted lime sludge in the extinguisher (EVL) and the number of kilos of added lime (EVH), or the selected setting points on the load cells 7, ie the setting points on the scale selected. The concentration of completely slaked lime is finally determined by the number of kilograms of water selected at the last set point (EVHH). The number of kilograms of water selected at the last set point (EVHH) is decisive for the concentration of completely slaked lime.

The load cells 7 generate five operating contacts for use in sequence: - at 2 EVHHH Filling of water to the upper level. - at 2 EVHH Achieved amount of filled rinsing water. - at 2 EVH Amount of added lime reached. - at 2 EVL New extinguishing level reached before new extinguishing. - at 2 EVLL Mixer is stopped.

Completely slaked lime is sent to the storage tank 3 through the valve 22 by means of a motor. The motor is preferably equipped with a safety switch and a service facility.

At the start, the extinguisher 2 is filled manually with 400 l of water, followed by 120 kg of lime while stirring. When the mixture has reached a stable temperature of about 80 ° C, detected by a temperature measuring element, automatic operation can start and water is added to a mixing weight of 1200 kg, giving a 10% sludge with a temperature of about 30 ° C.

The extinguisher can now be emptied to a predetermined weight of, for example, 600 kg. This is followed by an interruption of 30 s for return from, for example, the pump. It is important that the control system can register the actual value of the batch and is tarred to 0 kg, which is necessary as inertia in the system can lead to a risk that fl or fewer chemicals than predetermined are added to the extinguisher.

With automatic control, when the weight of the extinguisher 2 is 600 kg or a new calculated value based on the temperature control and after a pause of 30 s, the extinguishing process will start if it is not already running and the valve 22 will be closed.

Damper valve 12 in the extinguisher cover receives an opening signal and is confirmed in an open position by limit switch, the opening signal is transmitted to the valve 17 and a vacuuming unit 15 is started. After a time delay of 5 s, the throttle valve 11 is opened at the outlet end of the screw conveyor 6 and confirmed as open by a limit switch. A rotation monitor checks that stirring has started and an alarm is issued if this is not the case or if the valve is not open after the command. If stirring stops, valve 9 opens and the extinguisher is completely filled with water and the process is stopped.

The screw conveyor 6 is started 5 s after a limit switch has confirmed that the valve 11 is in an open position, and starts the timer for normal dosing time, for example 180 s. The correct dosing time is set when initiating the system. If the time is exceeded by 100% (360 in this example), the air stimulator will be opened and closed in a fixed cycle (open for about 0.5 s every 30 s) starting in the pause section and limited to 180 s. If the predetermined weight in the mixer still not reached, the cycle will be interrupted because the storage tank signals a low level and an alarm is issued.

The screw conveyor 6 is kept running until the required amount of lime (120 kg) has been weighed in. 1 s after the screw conveyor has stopped, the damper valve 11 closes. 10 s after the valve is confirmed as closed, a solenoid valve opens for 3 s for air to the output vibrator. The throttle valve 12 closes for 20 s after the throttle valve 11 is confirmed as closed, and a limit switch checks that the valve is closed. When the valve has closed, the weight is recalibrated to 0 kg. An alarm sounds if the valve is not closed after the command.

For immediate cleaning of the extinguisher 2 before the next extinguishing, after said recalibration of the load cell assembly 7, a number of valves are opened for a certain period of time for supplying rinsing water to the respective nozzles, in that the rinsing water is fed sequentially via each valve to the associated nozzle (s). predetermined amount of flush water is reached in the extinguisher 2. For example, 5 s after the throttle valve in the extinguisher 2 has signaled closed, the first flush water valve 25 with a nozzle is opened for 10 s, after which the first valve 25 is closed and the second valve 26 is opened for flushing water with three nozzles for 8 s, after which the second valve 26 is closed and the third valve 27 is opened for flushing water with three nozzles on the opposite side, until a total predetermined amount of flushing water has been weighed in by the extinguisher itself, for example 20 kg.

As shown in the figure, the first valve 25 controls the supply of water to one or two nozzles via a pipe 28, while the second valve controls the supply of water to one or two nozzles via a pipeline 29 and the third valve 27 controls the supply of water to a nozzle. or fl your nozzles via a pipeline 30. Preferably, nozzles are located on opposite sides of the extinguisher, for example the nozzles may be located in half of the extinguisher or in the entire perimeter of the extinguisher with, for example, the same or different mutual gap. 20 s after valve 12 is closed, the closing signal is delivered to the valve 17 and the vacuuming 15 is stopped. After stopping the screw conveyor, the adjustable switch-off time begins, for example 10 min. The selected switch-off time and its course must be indicated to the operator.

At the end of the extinguishing time, water is fed through the valve 8 and through the flushing nozzles 24 for 15 s. Thereafter, 1180 kg of dilution water (calculated from the second O-calibration which has already added 20 kg of water) is fed through the valve 9, which gives temperature of 30 ° C. With an error in the amount of lime added that is over +2%, the amount of dilution water is adjusted.

The temperature in the extinguisher is monitored by a temperature measuring element. If a temperature of 83 ° C is not reached during the quenching process, an additional 15 kg of the final sludge is discharged, thereby reducing EVLL to 485 kg or vice versa if the temperature is too high (88 ° C) to 515 kg.

If the temperature during the extinguishing process rises above 96 ° C, the valve 8 is also opened, the extinguisher is filled with water to full level EVHHH, the process is interrupted and an alarm is issued, without stopping the stirring.

As previously described, for the production of a 10% lime sludge, 60 kg of lime and 600 kg of water are required. The total level will vary depending on the temperature control. The final degree of concentration of the lime sludge determines the temperature of the sludge to which the lime is added for the next quenching.

If a lime sludge with a higher degree of concentration is desired, the quenching must take place at a higher initial temperature. If a lower degree of concentration is required, for example at the place of use, the sludge should be diluted outside the extinguisher, for example by proportional dosing between water and lime solution in the pipeline after the storage tank. Addition of water can be regulated with a fl fate meter and a control valve. Alternatively, measured amounts of water can be added to the storage tank at the same time as the extinguisher, from full weight in smaller batches, for example four, adds proportional amounts of lime sludge to the storage tank. 10 15 20 25 30 35 534 692 8 After the extinguishing time has elapsed, the level in the storage tank is checked and when this is reduced to EVLL, the valve 22 is opened and the batch is emptied into the storage tank.

Finished lime sludge is temporarily stored in the storage tanks 3 which are equipped with a level gauge in the form of a pressure sensor and also one or two mixers. The tank can generate signals for regulating the extinguishing sequence. The level signal generates two operating contacts for use in the sequence and also two signals for alarms at low and high levels, respectively, and a signal for starting pumps. - at 2 EVL: Extinguishing can be initiated. - at 2 EVLL: Signal for receiving a new batch from extinguisher. - at 2 AHH: Alarm, level too high. Valve closes. - at 2 AL: Alarm, level too low. - at 2 ALL: Alarm, very low level. Pumping out of tank 3 is stopped.

The mixer must work continuously and be monitored by means of PLC. An alarm is issued in addition to the stop.

One or two pumps are used for dosing the sludge. The pumps are arranged "standby" for each other and can be reset manually. Sealing water is added to the pumps' stuffing box through solenoid valves and has a built-in circuit breaker to release water if the sealing water does not appear for more than 3 minutes after start, an alarm is sounded and the pumps stop. The same will happen if sealing water is absent for three minutes during operation. In addition, each pump is equipped with a fl fate detector and a pressure sensor mounted in the pipe on the pressure side of the pumps. If these do not register an amount of water and pressure after 15 s, an alarm is issued. If the water and pressure are absent for another 15 s, the pumps will stop. A flow meter is used to measure the amount of sludge from the storage tank to the sand filter. This unit of measurement sends a 4-20 mA signal back to one or more of your frequency converters. Bottom set is emptied from the storage tank through a manually operated bottom valve.

In the present method, a system with a number of extinguishers 2 can be used for batch quenching of burnt lime, as previously mentioned above, to prevent accumulation of limestone in extinguishers, tanks and the system. 15 20 534 B92 9 In accordance with the invention, a first extinguisher 2 shall be discharged completely extinguished and diluted lime sludge, produced according to the method above, where the extinguisher is emptied according to the weight principle proportional to the water through the plant, without using intermediate buffer or dosing tanks, until a predetermined sludge weight mass remains. This slurry mass is used for mixing with the next batch. A second extinguisher in the system, which is ready for its emptying sequence, begins to discharge completely extinguished and diluted lime sludge, also produced according to the method above, according to the weight principle proportional to the water throughput of the plant, until a predetermined sludge mass remains, which is used for mixing with the next batch . The second extinguisher starts mainly when the first extinguisher has finished its emptying, or when the emptying speed of the first extinguisher has reached a predetermined level.

After rinsing with rinsing water via valves at each extinguisher, production of a new batch is started which is ready for its emptying sequence when the active extinguisher has finished its emptying. The flushing is done as described above in that a number of valves are opened after fixed periods of time for adding flushing water to the respective nozzles, whereby flushing water is fed sequentially via each valve to the associated nozzle or nozzles, until a finite amount of flushing water is reached in the extinguisher. Flush water is fed until the total amount of flush water is weighed.

Claims (2)

20 534 B92 10 Patent claims Method for continuous and proportional addition of lime to a water-permeable fl destiny in a plant, where a number of extinguishers (2) are used for batch quenching of burnt lime, and in which lime sludge with a higher degree of fineness and prolonged sedimentation is produced, characterized in that - a first extinguisher empties completely extinguished and diluted lime sludge according to the weight principle proportional to the water flow of the plant, until a predetermined sludge mass is left, which is used for mixing with the next batch, - a second extinguisher, which is ready for its emptying sequence, begins to empty completely extinguished and diluted lime sludge according to the weight principle proportional to the water throughput of the plant, when the first extinguisher has finished emptying, until a predetermined sludge mass remains, which is used for mixing with the next batch, and - after flushing with flushing water via valves at each extinguisher starts production of a new batch, which is ready for its emptying sequence when the active extinguisher has finished emptying. Method according to Claim 1, characterized in that the respective extinguisher is emptied directly to the water flow through the plant, without the use of intermediate buffer or dosing tanks.